This invention relates to a photosensitive composition which is useful as a resist composition to be employed for fine working in the manufacturing process of a semiconductor device, and in particular to a photosensitive composition which is particularly suited for use in a fine working where a short wavelength light such as ultraviolet ray, deep UV beam, KrF excimer laser beam having a wavelength of 248 nm, ArF excimer laser beam having a wavelength of 193 nm, fluorine laser beam, electron beam or X-ray is employed as an exposure energy source.
In the manufacture of electronic parts such as a semiconductor device, a fine pattern is formed by making use of a photolithographic technique. In this fine working technique, a thin film, i.e. a photoresist film is first formed by coating a resist composition on a semiconductor substrate for instance. The photoresist film thus formed is then exposed to light through a prescribed mask pattern, and subsequently subjected to various treatments including a development and a rinsing, thereby forming a resist pattern. This resist pattern is then utilized as an etching resistant mask in a dry etching process, and the exposed surface portions of the substrate, etc. are etched away to form a pattern of fine line or window thereby obtaining a desired pattern. Finally, the resist pattern remaining on the substrate is removed through dissolution, thus forming a patterned substrate.
In view of a trend in recent years to further increase the integration of semiconductor elements, it is now demanded to develop a working technique which enables to form a still finer pattern. In view of such a demand, the employment of a light source of shorter wavelength in photolithography is now being studied. For example, a method for forming a finer resist pattern employing as a light source an ArF excimer laser (193 nm in wavelength) or the quintuple harmonic of YAG laser (218 nm in wavelength) has been developed. It has now become possible through the employment of this method to form a wiring pattern having a minimum line width in the order of submicron. However, there is still a trend to further increase the fineness of wiring pattern.
By the way, since a dry-etching process utilizing plasma has been developed for the fine working of a substrate, etc., it is now demanded, with a view to effectively utilize this fine working process, to employ a resist which is excellent in dry-etching resistance in the formation of a resist pattern.
With this respect, there is known a photosensitive material comprising an aromatic compound as a resist material. Namely, many kinds of resist material comprising a phenolic resin as a base material have been developed up to date.
However, these resist materials generally exhibit a high absorption of the light of short wavelength when they are employed in a lithography where the light of short wavelength as mentioned above is employed as an exposure light source. Therefore, it is impossible, because of this prominent light absorption, to allow the exposure light to reach deep enough to the bottom portion of the resist film at the light exposure step. As a result, it has been very difficult with these conventional resist materials to form a fine pattern.
On the other hand, the employment of polymethyl methacrylate (PMMA) having no aromatic ring is also studied as a resin exhibiting a low light absorption. However, this polymethyl methacrylate is accompanied with a problem that this compound is poor in dry-etching resistance.
It is now studied to employ a simple aliphatic cyclic compound as a base resin. However, the aliphatic cyclic compound is accompanied with problems that it is not only poor in solubility and alkali-developing property, but also insufficient in dry etching resistance.
As mentioned above, in order to of realize a fine pattern of sub-quarter micron in line width, it is required that the photosensitive material is minimal in light absorption and that the resist pattern obtainable from the photosensitive material has a sufficient dry-etching resistance.